1. Technical Field
The present technology relates to a pneumatic tire and particularly relates to a pneumatic tire having enhanced tire braking performance on ice.
2. Related Art
Tread patterns in which a plurality of sipes is disposed in a tire pattern in order to enhance braking performance on ice of studless tires are known. Also, in recent years, there has been a tendency toward increasing the number of sipes. However, sipe density is increased as a result of increasing the number of sipes, and while this leads to an increase in the number of edges, it also leads to the problems of the overall rigidity of the block declining and braking performance on ice declining.
Therefore, technology has been proposed in which collapsing of portions of a block that are sandwiched by sipes is suppressed and a decline of block rigidity is suppressed by disposing recesses and protrusions within the sipes (Japanese Patent No. 3180160).
However, in cases where a plurality of blocks are provided in a tread portion by a plurality of vertical grooves extending in the tire circumferential direction and a lateral groove extending in a direction that intersects the tire circumferential direction, and a plurality of sipes spaced in the tire circumferential direction are provided in a tread surface of the blocks, at an area located at edges of the blocks in the tire circumferential direction, a portion of the blocks is partitioned by the sipes and the lateral groove, and at areas other than the edges in the tire circumferential direction, a portion of the blocks is partitioned by adjacent sipes.
Therefore, the portion of the blocks located at the edges in the tire circumferential direction is partitioned by the sipes and a lateral groove having a width greater than that of the sipes, and, compared to portions of blocks located at other areas that are sandwiched by adjacent sipes, these portions only engage with a portion of an adjacent block on one side and, thus, are prone to collapsing.
When there are portions in blocks partitioned by vertical grooves and lateral grooves that are more prone to collapsing than other areas or, rather, when there are portions of the block that collapse more than other areas, it is difficult to enhance the edge effect and enhance braking performance on ice.